1. Technical Field
The disclosure relates to a heat dissipating device, and particularly to an electric fan having an improved fan impeller and a heat dissipation device having such a fan.
2. Description of Related Art
With continuing development of electronic technology, a heat-generating electric component such as CPU (central processing unit) is generating more and more heat that requires immediate dissipation. Generally a heat sink is thermally attached to the CPU, and an electric fan is mounted on the heat sink for providing an airflow to cool the CPU.
A typical electric fan includes a fan impeller having a cylindrical-shaped sidewall and a plurality of blades extending radially from the sidewall of the fan impeller. A bottom wall of the fan impeller facing the heat sink is flat and is perpendicular to the sidewall. When the blades rotate to generate an airflow flowing to the heat sink, the bottom wall of the fan impeller prevents the airflow from flowing to a center of the heat sink under the fan impeller of the electric fan. Accordingly, an amount of the airflow at the center of the heat sink is approximately zero. However, the center of the heat sink is usually attached to the heat-generating electric component and has more heat than other portion of the heat sink. Thus the airflow provided by the typical electric fan cannot efficiently dissipate heat of the heat sink absorbed from the heat-generating electric component.
Therefore, a heat dissipation device having an improved fan is desired to overcome the above describe shortcomings.